1. Field of the Invention
This invention is directed to heavy construction attachment systems, in particular, to a system incorporating major disassembable units and to the units of the system.
2. Background of the Invention
In the construction industry, concrete foundations are commonly manufactured by using formwork into which concrete is poured. This formwork usually consists of re-usable wood and aluminum composite struts and joists which provide a supporting crib-work or lattice for the actual sheathing members onto which the concrete is poured. The sheathing frequently consists of plain or paper faced plywood members. Thus, a substantial plywood sheathing sheet for example 3/4 inch ply, having a replaceable paper liner as the casting surface, is usually nailed to an underlying supporting joist having an inset nailing strip. After the concrete has set, the underlying formwork lattice and plywood is removed. Frequently the plywood has to be torn down, owing to the entrainment of the attachment nails into the concrete. Similarly, the face of the plywood may be Penetrated by the concrete and become damaged. The wood nailing strips of the supporting laticework will become damaged over time due to repeated re-use and will have to be replaced. Considerable expenditures in material and labour costs are therefore involved, and valuable resources are used up.
The present method of manufacturing concrete foundations also has a drawback in that seam outlines of the 4.times.8 foot sheathing sheets, caused by misalignments, gaps and penetrating cement flashings must be ground away where a smooth finished surface is required.
The use of hook and loop elements for the purpose of joining flexible elements is not new. The garment and footwear industries have for many years employed a particular hook and loop type attachment material, commonly referred to by the trade mark VELCRO, for securing the adjacent surfaces of clothing and footwear. However, this material is limited both by the presently available widths, which do not exceed four inches, and by the maximum anchoring force developed by the plastic hook elements. Furthermore, prior usage appears to have been concentrated on the application of this type of fastener in areas where a peeling. wave-like relative movement can be used to attach and detach a pair of complementary hook and loop surfaces, as when opening a garment or a shoe flap or on the installation of decorative, non-structural panels such as shown in Wilson, U.S. Pat. No. 4,744,189 issued May 17, 1988 or room dividers such as shown in Curatolo, U.S. Pat. No. 4,090,335 issued May 23, 1978.